Are Cavities Contagious?

Mar 15, 2021

No parent wants to hear that their child has a cavity. After all, the team at Stellar Kids Dentistry in Mukilteo, Mill Creek, and Everett, Washington, knows how hard you work to keep your little one’s teeth healthy and cavity-free. That’s why you might be surprised when your family’s pediatric dentist tells you one of your children needs a cavity filling.

Tooth decay is extremely common in people of all ages. While brushing and flossing twice a day minimizes your risk of getting a cavity, good oral hygiene can’t protect against tooth decay that’s spread from another person.

Now, you might be wondering, did I read that wrong? If so, you’re not alone. Not many people realize that cavities can spread inside your own mouth, as well as from person to person. 

Below, let’s discuss exactly what cavities are and how they can spread to your little one’s mouth, even if you’re doing everything you can to avoid them.

What are cavities?

Cavities are tooth decay caused by plaque, a sticky film of bacteria that clings to teeth. When plaque sticks to your child’s teeth, it releases toxins that eat away at their protective tooth enamel. Eventually, this deterioration results in tiny holes in their teeth. These are cavities.

Without treatment, cavities continue to grow. They can even spread to other teeth in your child’s mouth. If a cavity grows large enough, it puts your little one at risk of early tooth loss and gum disease.

How do cavities spread between people?

The bacteria that causes cavities is spread through saliva. If your child exchanges saliva with another person who has cavities, that cavity-causing bacteria can end up growing in their own mouth. Believe it or not, cavities spread from one person to another more easily than you think.

How can I prevent cavities from spreading to my child?

Certain situations in which tooth decay can spread from person to person include:

Sharing food and drinks

Each time you eat and drink, your saliva ends up all over your utensils and glasses. That’s why most of us avoid sharing food and drinks when they know the other person is sick or feeling unwell. We don’t want their virus or infection to spread to us. 

Much like the way viruses spread through saliva, so does cavity-causing bacteria. Something as small as sharing a glass of milk with a friend leaves your child vulnerable to the bacteria that causes cavities.

Storing toothbrushes together

Many families store their toothbrushes together. While this may be convenient, it’s not hygienic. If you or a loved one has tooth decay, the saliva left behind on your toothbrush can carry bacteria over to your child’s toothbrush

You can significantly minimize your child’s risk of cavities by storing your family’s toothbrushes in different containers. In addition, make sure you’re replacing your family’s toothbrushes at least once every 3-4 months to prevent the buildup of bacteria.


Because kissing is a direct exchange of saliva, it’s one of the most common causes of cavities spreading from person to person. Babies, in particular, don’t have fully developed immune systems, which increases their risk of bacterial infections. 

If you or a close family member has tooth decay, try to avoid kissing your baby directly on the mouth to prevent cavities from spreading.

With an experienced team of dentists, Stellar Kids Dentistry can help keep your child healthy and cavity-free. Call the location nearest you or schedule an appointment online to learn more!